1. Field of the Invention
The present invention relates to an operating device in a vehicle provided with a pair of continuously variable transmissions, comprising a pair of right and left continuously variable transmissions such as hydrostatic continuously variable transmissions, belt-type continuously variable transmissions, cone-type continuously variable transmissions, and frictional-type continuously variable transmissions, for controlling the vehicle speed and conducting a steering by connecting the right and left continuously variable transmissions to right and left driven wheels, respectively.
2. Description of the Prior Art
Such a steering control device in a vehicle provided with a pair of continuously variable transmissions has already been disclosed in Japanese Patent Publication No. 57-25428, Japanese Utility Model Publication No. 49-38826, Japanese Patent Application Laid-open No. 57-950, and Japanese Utility Model Publication No. 40-31219.
Steering characteristics at the time of turning of a vehicle include, among others, a neutral steering state in which the speed of an inner wheel of the driven wheels during turning and the speed of an outer wheel of the driven wheels during turning have a predetermined ratio relative to each other that is suited to the turning radius so that a slipping tendency does not occur in either of inner and outer wheels, an under-steering state in which the speed of the inner wheel has a higher ratio to the outer wheel speed than that in the neutral steering state, an over-steering state in which the outer wheel speed has a higher ratio to the inner wheel speed than that in the neutral steering state, and a stationary turning state in which the inner wheel speed during turning is zero.
In the mentioned known operating devices, however, the steering characteristics that are set on the basis of the operation of the steering angle setting means can not be varied, and thus a favorable steering characteristic cannot always be obtained following changes in the vehicle speed.
Further, in the known operating devices, the operation of vehicle speed setting means and the operation of steering angle setting means are mixed in a speed change operating device, and transmitted to the transmission and therefore, if the operation of vehicle speed setting means interferes with the operation of steering angle setting means, or the operation of steering angle setting means interferes with the operation of vehicle speed setting means, there is a problem that the vehicle traveling operation becomes complicated, or the travel operation feeling is impaired.
Furthermore, in the known operating devices, unless the speed change operating device and transmission are configured and located rationally, not only the balance of weight distribution and space distribution in the lateral direction of the vehicle body is worsened, but also a link mechanism for transmitting the motion of a speed change control member of the speed change operating device to a speed change control member of the transmission is complicated and extended in length, and accurate speed change control may become difficult because a deflection or backlash is produced.
It is a first object of the invention to always obtain a favorable steering characteristic regardless of vehicle speed changes.
It is a second object of the invention to reliably operate the speed change operating device, while avoiding interference between the operation of vehicle speed setting means and operation of steering angle setting means.
Further, it is a third object of the invention to realize an accurate speed change control by rationally disposing the speed change operating device and transmission in a vehicle provided with a pair of continuously variable transmissions, thereby improving the balance in the lateral direction of the vehicle body and designing the link mechanism in a compact form.
To achieve the first object, the invention provides an operating device in a vehicle provided with a pair of continuously variable transmissions, the vehicle comprising: left and right driven wheels connected to the pair of continuously variable transmissions, respectively; a vehicle speed setting means for setting a vehicle speed; and a steering angle setting means for setting a steering angle; in which outputs of the continuously variable transmissions are increased and decreased at substantially identical rotational numbers to each other based on an operation of the vehicle speed setting means, and the outputs of the continuously variable transmissions are increased and decreased at different rotational numbers from each other based on an operation of the steering angle setting means, thereby varying wheel speeds of the driven wheels so as to control the vehicle speed and to conduct a steering, wherein the operating device includes a steering characteristic changeover means for changing over speed increasing and decreasing characteristics of the pair of continuously variable transmissions based on the operation of the steering angle setting means in accordance with the vehicle speed.
According to the above arrangement, since the steering characteristic changeover means changes over the acceleration and deceleration characteristics of the pair of continuously variable transmissions which are based on the operation of the steering angle setting means, depending on the vehicle speed, a favorable steering characteristic suited to the vehicle speed is obtained both at low vehicle speed and at high vehicle speed. Once the vehicle speed is set by the vehicle speed setting means, the turning speed and turning radius can be set to an ideal state by operation of the steering angle setting means, and therefore it is possible not only to achieve a stable turning radius with a small slip rate of the inner and outer wheels with respect to the ground but also to facilitate the vehicle travel operation, thus enhancing the working efficiency and lessening the fatigue of the driver.
To achieve the second object, the invention provides an operating device which includes the above arrangement, and further comprises: a transmission system including the pair of continuously variable transmissions for changing the rotational numbers of the left and right driven wheels; and a pair of speed change follower members provided in the transmission system wherein a speed change operating device is provided for driving the speed change follower members at an identical phase based-on an operation of the vehicle speed setting means, and for driving the speed change follower members at different phases based on an operation of the steering angle setting means; wherein the speed change operating device comprises: a pair of speed change driving members connected to the pair of speed change follower members; a pair of first speed change operating members which are pivotally supported, through a longitudinal shaft, on a lateral shaft which is operatively associated with the operation of the vehicle speed setting means for longitudinal swinging movement, the first speed change operating members being capable of longitudinally swinging integrally with the lateral shaft and capable of laterally swinging about the longitudinal shaft; a link member for connecting the pair of first speed change operating members to the pair of speed change driving members; a second speed change operating member operatively associated with the operation of the steering angle setting means for laterally swinging movement; and a mixing member which transmits a lateral swinging movement of the second speed change operating member to the first speed change operating members for laterally swinging the first speed change operating members, and which restrains a longitudinal swinging movement of the first speed change operating members from being transmitted to the second speed change operating member.
With this arrangement, even if the first speed change operating member is swung longitudinally about the lateral shaft by the operation of the vehicle speed setting means, the longitudinal oscillation of the first speed change operating member is prevented from being transmitted to the steering angle setting means by the mixing member. Moreover, even if the second speed change operating member is swung laterally by the operation of the steering angle setting means, it merely causes the first speed change operating member to oscillate laterally about the longitudinal shaft through the mixing member, so that its lateral oscillation may not be transmitted to the speed change setting means. It is hence possible to transmit the operation of the vehicle speed setting means and operation of steering angle setting means to the transmission while mixing the operations but avoiding their mutual interference, thereby preventing complication of steering operation and worsening of steering feeling.
To achieve the third object, the invention provides an operating device which includes the above arrangement and further characterized in that a transmission system including the pair of continuously variable transmissions and a speed change operating device for controlling speed change characteristics of the continuously variable transmissions are mounted on a vehicle body frame; wherein a speed change control member provided in the speed change operating device and another speed change control member provided in the transmission system are connected together by a link member wherein the speed change operating device is disposed in a lower portion of a seat provided at a substantially central portion of a vehicle body in both longitudinal and lateral directions, the transmission system is disposed in a rear of the speed change operating device at a position substantially centrally in the lateral direction of the vehicle body, and the link member is disposed substantially along the longitudinal direction of the vehicle body.
According to this arrangement, not only the waste space beneath the seat can be effectively utilized, but also the balance of weight distribution and space distribution in the lateral direction of the vehicle body can be enhanced, and moreover the link member for connecting both the speed change control members can be of a minimum length, so that formation of deflection or backlash can be effectively prevented.
The above and other objects, features and advantages of the invention will become apparent from preferred embodiments taken in conjunction with the accompanying drawings.